Akio Doi

Polyhedral approximation approach to molecular orbital graphics

Abstract Interactive molecular orbital display and manipulation system is developed under the concept of polyhedral approximation of equivalued surfaces of orbital and density functions. Two new methods for generating polyhedral data, lscell-based’ and ‘propagation’ methods, are presented. The use of stored polyhedral data largely simplifies the shaded-image synthesis, direct manipulation, and animation display of molecular orbitals. Manual overlay of frontier orbitais is useful to estimate the geometries of chemically reacting molecules.

Clinical planning support system-CliPSS

Clinical planning support system (CliPSS), which is software developed to support neurosurgical planning and to enable a surgeon to generate 3-D computed images interactively and simulate sterotactic surgery on them, is discussed. The basic functions of CliPSS, involving section display, editing, extraction, and rendering, are reviewed. A method of thinning the volume of polygonal data for a surface-rendered image, which improves CliPPSs performance and interactivity, is presented.<<ETX>>

High-speed image display algorithm for 3-D grid data

In this paper, we propose a high-speed and direct imaging algorithm for constructing equi-valued surfaces from 3D grid data in scientific and enneering fields. Our basic idea is to generate and draw polygons simultaneously by processing the cells spanned by grids in order of decreasing distance from the current viewpoint. Equi-valued surfaces are generated in five tetrahedrons into which the cells are subdivided, and are sent to a graphics device. The execution order of each of the tetrahedrons is identical and determined by the current viewpoint. Since the algorithm does not need a store of intermediate polyhedral data, depth calculation, or depth buffer memory for hidden surface removal, the user can get a quick response to changes of the view direction and of the surface constant C in interactive graphics. This algorithm is particularly powerful for imaging multiple surfaces associated with multiple surface constants in semi-transparent display.

Surgical-planning support system for stereotactic endoscopy

We describe a neurosurgical planning support system that we developed on a workstation. It enables a surgeon to generate useful 3-D images interactively and to simulate surgery on the computed images pre-surgically to confirm the optimum parameters for the instruments used in stereotactic surgery. In particular, we introduce two techniques for implementing indispensable functions in systems like this. One is an algorithm that can detect boundaries in medical images, and the other is an algorithm that can reduce the volume of polygonal data for surface-rendered images. These techniques move our system a step toward clinical use.

Visualization of generalized multiple molecular surfaces

In order to visually assist researchers in designing new drugs and materials by computer, this paper extends the concept of molecular surfaces from the view of quantum chemistry, and present a practical method of rapidly generating semi-transparent multiple surfaces and visualizing surface inclusion relation. The proposed method is a hybrid method of the depth-buffer and list-sorting methods. The surface inclusion is detected by the order of oriented surfaces.

A cell‐transverse display algorithm for regular and rectilinear 3D grid data

This paper proposes an efficient direct imaging algorithm for constructing iso-surfaces from regular and rectilinear 3D grid data in scientific and engineering visualization. The basic idea is to generate and draw polygons simultaneously by processing the cells spanned by grids in decreasing order of distance from the current viewpoint. Iso-surfaces are generated in five or six tetrahedrons into which the cells are subdivided, and are sent to a graphics device or drawn into a frame buffer on the fly. The execution order of each of the tetrahedrons is identical and is determined by the current viewpoint. Since the algorithm does not need to store intermediate polyhedral data and does not require a depth buffer memory for hidden surface removal, it is applicable to a large quantity of data on a 3D grid, such as computed tomography (CT) data. It is also particularly powerful for semi-transparent display, because transparency calculation can be reduced to image compositing operations if the polygons are drawn in order of their z-depth from the current viewpoint.